U.S. patent number 4,287,142 [Application Number 05/952,732] was granted by the patent office on 1981-09-01 for process for the production of mineral wool products.
This patent grant is currently assigned to Rockwool International A/S. Invention is credited to Kjeld Holbek.
United States Patent |
4,287,142 |
Holbek |
September 1, 1981 |
Process for the production of mineral wool products
Abstract
A process for the production of mineral wool products comprising
admixing fine starting materials, a hydraulic binder, and an
inorganic material containing at least 75% SiO.sub.2 and having an
average particle size of less than 100 .mu.m to form a mouldable
mixture, moulding the mixture to form briquettes, heating the
briquettes to a temperature sufficiently high to form a melt and
converting the melt thus formed into a mineral wool product.
Inventors: |
Holbek; Kjeld (Lejre,
DK) |
Assignee: |
Rockwool International A/S
(Hedehusene, DK)
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Family
ID: |
8118226 |
Appl.
No.: |
05/952,732 |
Filed: |
October 19, 1978 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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811829 |
Jun 30, 1977 |
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Foreign Application Priority Data
Current U.S.
Class: |
264/37.28;
106/705; 106/709; 106/711; 264/211.11; 264/333 |
Current CPC
Class: |
C03C
1/026 (20130101); C03C 13/06 (20130101); C03B
1/02 (20130101); C03C 1/02 (20130101); C03C
1/002 (20130101) |
Current International
Class: |
C03B
1/00 (20060101); C03B 1/02 (20060101); C03C
1/02 (20060101); C03C 13/00 (20060101); C03C
1/00 (20060101); C03C 13/06 (20060101); C04B
035/14 () |
Field of
Search: |
;264/333,176F,37
;106/98 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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252109 |
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Aug 1962 |
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AU |
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205247 |
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Jun 1961 |
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SE |
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Primary Examiner: Parrish; John A.
Parent Case Text
This is a continuation of application Ser. No. 811,829 filed June
30, 1977, abandoned.
Claims
I claim:
1. A process for the production of mineral wool products which
comprises the steps of
(1) mixing together the following components: a finely divided
mineral-containing material, a hydraulic binder, an inorganic
material containing at least 75% by weight of SiO.sub.2 and being
in the form of particles having an average size of less than 100
.mu.m, and a waste material recycled from step (4),
(2) moulding the mixed components of step (1) to form
briquettes,
(3) heating the briquettes of step (2) to a temperature sufficient
to form a melt,
(4) spinning the melt of step (3) to form mineral wool and a waste
material mainly consisting of unfiberized particles of mineral
wool, and
(5) recycling said waste material of step (4) to the mixture of
step (1).
2. The process of claim 1 wherein said inorganic material is in the
form of particles having an average size of less than 50 .mu.m.
3. The process of claim 1 wherein said inorganic material is in the
form of particles having an average size of less than 1 .mu.m.
4. The process of claim 1 wherein said inorganic material is fly
ash.
5. The process of claim 1 wherein said inorganic material is
present in said mixed components of step (1) in an amount of up to
30% by weight.
6. The process of claim 1 wherein said mineral-containing material
is mineral wool.
7. The process of claim 1 wherein iron is added to the mixed
components of step (1).
Description
BACKGROUND OF THE INVENTION
This invention relates to a process for the production of mineral
wool products comprising admixing the starting materials in finely
divided form and a hydraulic binder to form a mouldable mixture,
moulding the mixture to form small bodies of a desired size (in the
following referred to as briquettes), heating the briquettes to a
temperature sufficiently high to form a melt and converting the
melt thus formed into a mineral wool product.
The specification of Swedish Pat. No. 205.247 discloses a process
of the above mentioned type and comprises the use of Portland
cement, clay or water glass as hydraulic binder to form the
briquettes. However, it has been found that when using such
briquettes, the melting conditions in furnaces which ordinarily are
used in the production of mineral wool products are not fully
satisfactory. This is due to the fact that the compressive strength
of such briquettes decrease significantly when the temperature of
such briquettes is raised to above about 500.degree. C. Therefore,
the briquettes tend to disintegrate and be converted into powder or
dust at high furnace temperatures. The presence of such fine
materials in the furnace adversely affects the melting process
because it counteracts the desired flow of air and flue gases
through the furnace. Thus, the presence of these fine materials
results in the formation of a large pool of melt having a high
temperature whereas it is desired to effect a gradual melting of
the surfaces of the briquettes so as to allow a continuous supply
of air and a continuous discharge of flue gases.
The object of the invention is to improve the melting conditions by
a process of the type described above.
SUMMARY OF THE INVENTION
The process of the invention is characterized in introducing into
the mixture of fine starting materials and hydraulic binder a fine
inorganic material containing at least 75% SiO.sub.2 and having an
average particle size of less than 100 .mu.m.
The introduction of a fine material having a high SiO.sub.2 content
into the mixture to be converted into briquettes presents the
surprising advantageous effect that during the heating of the
briquettes, SiO.sub.2 reacts with the starting materials and that
this reaction which causes the briquettes to maintain their form at
temperatures, i.e. at 500.degree. C. or above, at which the effect
of the hydraulic binder has significantly decreased. Thus, by using
an additive as defined above, the briquettes maintain their form
until an initial melting of the surfaces of the briquettes
starts.
Thus, the desired flow of gases through the furnace can be
maintained and a relatively short melting zone is obtained.
The fine SiO.sub.2 -containing material may be a commercially
available almost pure SiO.sub.2 powder which is sold under the
trade names "Cab-O-Sil" and "Aerosil" (registered trade marks).
Another suitable SiO.sub.2 -containing material is fly ash and in
particular fly ash obtained in the production of ferro silicon. The
SiO.sub.2 content of such fly ash is ordinarily above 90%.
As mentioned above, the average particle size of the SiO.sub.2
-containing material should be less than 100 .mu.m, preferably less
than 50 .mu.m and most preferable less than 1 .mu.m, because only
such fine particles have a sufficiently high reactivity to react
with the remaining components of the briquettes to prevent these
briquettes from disintegrating at the temperatures at which the
effect of the hydraulic binder starts decreasing.
The SiO.sub.2 -containing material is preferably used in an amount
of up to about 30% by weight of the dry weight of all components of
the briquettes. When the SiO.sub.2 -containing material is used in
admixture with Portland cement, it is ordinarily sufficient to use
about 5% SiO.sub.2 -containing material.
The process of the invention also presents the advantage that it
has permitted a more economical production of mineral wool and has
solved a serious environmental problem.
In the production of mineral wool large amounts of waste products
are formed. These waste products which correspond to 25-30% of the
starting materials consist partly of furnace slag and partly of
mineral wool and so-called pearls which are deposited on the bottom
of the spinner chamber in which the melt is converted into fibres.
The major part of these waste materials are relatively fine and
consequently they cannot be recycled to the furnace without causing
the problems discussed above. However, by admixing these waste
materials with the starting materials, hydraulic binder and
SiO.sub.2 -containing material, they can be introduced into the
furnace in a form which does not adversely affect the melting
process. Thus, the need of transporting these waste materials to
places in which they can be stored in nature is eliminated.
Since the costs of transportation and storage of these waste
materials are relatively high in many countries, the savings
obtained by avoiding such transportation and storage are
significant. Furthermore, the recycling of the waste materials to
the melting furnace reduces the consumption of raw materials.
The process of the invention has also made it possible to use many
starting materials which, due to their physical form, have been
found unsuitable for use in the production of mineral wool
products. Therefore, it is possible to avoid the traditional
troublesome quarrying of minerals, such as diabase, by blasting and
subsequent crushing and classification of such minerals to obtain
suitable starting materials for use in the production of mineral
wool.
Furthermore, the process of the invention permits the production of
mineral wool products of varying compositions because the
briquettes used as starting materials can be composed so as to
fulfill virtually any need.
The recycling of waste products in the production of mineral wool
products results in an iron deficiency because part of the iron
contained in the starting materials is reduced in the melting
furnace. This deficiency can be eliminated by adding to the mixture
of starting materials an extra amount of iron to compensate for
such reduction.
In a preferred embodiment of the process of the invention, the
briquettes are produced by admixing the fine starting materials,
the dry hydraulic binder, such as Portland cement, and the
SiO.sub.2 -containing material and by subsequently adding water to
the mixture thus formed.
The water-containing mixture is stirred and is then introduced into
moulds which are vibrated and left to stand. After about 24 hours
the briquettes formed can be removed from the moulds and after
about 3 days they can be introduced into a melting furnace. At that
time they have a compressive strength of about 60 kp/cm.sup.2 which
is considered to be sufficient.
The moulding of the briquettes can also be effected by pressing,
rolling or extrusion.
The invention will now be described in further detail with
reference to the following non-limiting example.
EXAMPLE
In order to determine the compressive strength of briquettes for
use in the process of the invention and briquettes for use in the
prior art process described above at different temperatures, a
number of test briquettes having the dimensions
10.multidot.10.multidot.10 cm were prepared. The composition of
these briquettes and their compressive strength after heating to
various temperatures are set forth in the following table.
TABLE ______________________________________ Sample No. 1 2 3 4 5
______________________________________ Composi- Mineral wool 40 40
40 40 40 tion, % Waste cement 10 10 10 10 by weight Calcium
silicate.sup.(1) 10 Ash from ferro- silicon pro- duction 10 Glass
powder.sup.(2) 10 Gravel (0-4 mm) 40 50 40 40 50 Water
glass.sup.(3) 10 Compres- 20.degree. C. 102 81 >150 23 53 sive
strength, 500.degree. C. 74 93 >150 20 38 kp/cm.sup.2, after 14
about days sto- 700.degree. C. 59 44 150 18 20 rage and heat about
treat- 900.degree. C. 42 38 125 20 13 ment at a tempera-
1100.degree. C. 0 0 65 0 14 ture of
______________________________________ .sup.(1) Made from a mixture
of lime and sand. .sup.(2) Crushed glass wool. .sup.(3) The
briquettes were dried in a drying box and subsequently stored.
As will appear from the table, the strength properties of the
briquettes for use in the process of the invention are clearly
superior to those of the prior art briquettes.
The briquettes prepared from Sample No. 3 were molten at about
1500.degree. C. and were converted into mineral wool in a mineral
wool spinner.
The mineral wool obtained was of the same quality as mineral wool
prepared without the use of briquettes.
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